Drill string stabilizer



Oct. 4, 1966 G. T. CARTER 3,276,824

DRILL STRING YSTABILIZER Filed sept. 13, 196s 2 sheets-sheet 1 p5?? MS@rra/@Vga G. T. CARTER DRILL STRING STAB ILIZER Oct. 4, 1966 2Sheets-Sheet 2 Filed Sept. 13, 1963 United States Patent O 3,276,824DRILL STRING STABILIZER George T. Carter, Houston, Tex., assignor toGrant Oil Tool Company, Los Angeles, Calif., a corporation ol CaliforniaFiled Sept. 13, 1963, Ser. No. 308,825 4 Claims. (Cl. 308-4) Thisinvention relates to drill string stabilizers, and more particularly toa drill string stabilizer assembly adapted to be removably aixed to thedrill collar portion of the drill string.

Drill string stabilizers are well known as tools for cushioning lateralshock loads and lateral movements of the drill collar or drill string inrotary drilling operations. One common type is that which acts as abearing in which the drill string rotates. Deflection under the weightsupplied by the drill string to the bit makes it very diflicult to drilla hole which does not deviate from the vertical. To supply as muchweight as possible directly above the bit, more drill collar sectionshave been used in recent years. Such drill collars are thick-walledsections of heavy pipe with flush heavy joints or couplings whichincrease the rigidity of the drill string and reduce the Wobbling of thedrill bit. Additionally, drill collars are of suicient weight thatl thecompressive force necessary on the bit is exerted by the collar sectionwhile the drill pipe portion of the string remains in tension. Variousstudies have been made which dictate the use of stabilizers at specieddistances above the bit for various drilling parameters. For example,when the hole becomes inclined or crooked, the drill string makescontact with one side of the hole, causing the bit to make unevencontact with the bottom of the hole, thereby increasing the crookednessor deviation. These studies, of which the Woods-Lubinsky report is anexample, indicate the exact footage above the drill bit at whichstabilizers should be positioned to minimize deviation. Thus,stabilizers function toY center the drill string relative to the wallsof the hole being drilled to thereby cause even contact of the bit withthe bottom of the hole and provide for straighter and faster drilling.

In the prior state of the art, such stabilizers of the bearing typeinclude a tool body adapted to be inserted between sections of the drillcollar portion of the drill string, and a rotatable portion termed theboot or bushing which is rotatably mounted upon the tool body in orderthat the body may rotate within the bushing while the bushing remainsstationary relative to the hole. The tool body in turn includes acylindrical journal or mandrel section having an outside diametermatable with the inside diameter of the boot, and a length greater thanthe length of the boot such that when the boot is in place thereon, theboot can freely rotate;

At the upper end of the mandrel section there is conneeted a top collarhaving a diameter sufiicient to provide a transverse shoulder to limitthe upward travel of the boot along the mandrel. A lower transverseshoulder is provided by the tool body to limit the downward travel ofthe boot along the mandrel. The top colla-r and mandrel section havesuitable ush threaded joints for connection into the drill stringbetween adjacent sections of drill collar.

In nomal operation, the drill string moves downwardly with respect tothe boot such that the boot rotates in bearing contact with the uppershoulder. Means are usually provided for locking the boot intononrotating engagement with the lower shoulder to allow for washoveroperations. Thus, a series of indentations are typically provided in thebearing surface of the lower shoulder. These indentations are matablewith ratchet-like indentations in 3,276,824 Patented Oct. 4, 1966 thelower end surface of the boot. When the boot is forced into contact withthe lower shoulder it cannot rotate in one direction and a washover toolcan be utilized to remove the boot from the tool body.

From the foregoing it can be seen that prior art stabilizers are adaptedonly to be inserted between sections of drill collar, which sections areof standard length. The positioning of the stabilizer is thus limited topoints above the drill bit where a joint occurs between sections oidrill collar.

Accordingly, it is a primary object of the present invention to providea drill string stabilizer which is adapted to be positioned at any pointalong the length of the drill collar.

It is another object of the present invention to provide an improveddrill string stabilizer assembly which can be inserted on the drillcollar without causing another tool joint or connection therein.

Another object of the present invention is to provide a drill stringstabilizer which can be changed in location on the drill collar sectionof a drill string without disassembly of the drill collar sections.

Yet another object of the present invention is to provide an improvedstabilizer which is removably ailixed at any point along the length ofthe drill collar without damage to the collar.

The present invention comprises a drill string stabilizer assemblyhaving a bushing section adapted to be rotatably mounted upon theexterior surface of a drill collar section. An upper shoulder assemblyis removably affixed to the exterior surface of the drill collar andprovides a transverse shoulder which limits the longitudinal movement ofthe bushing along the drill colla-1 in one direction and a lowershoulder spaced from the upper shoulder by -a distance greater than thelength of the bushing. y

Such a stabilizer allows the drill collar to rotate within the bushingsection which is attached directly to the drill collar without weldmentsof any kind and which is limited in vertical travel on the drill collarby means of these special shoulder assemblies. In this manner thestabilizer may be randomly spaced along the drill string, as desired,and does not need extra connections or the insertion of bodies withinthe drill string. By use of the present invention better prediction andcontrol of hole direction and deviation can be obtained, and since nostabilizer body is required the freight-handling problem is reduced.

The novel features which are believed to be characteristic of t-heinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will be better understoodfrom the following description considered in connect-ion with theaccompanying drawing in which a presently preferred embodiment of theinvention is illustrated by way of eX- ample. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only, and is not intended as a deiinition of the limitsof the invention.

In the drawings:

FIGURE l is a view in elevation of a drill string with a stabilizerassembly, in accordance with the present invention, in place on thedrill collar;

FIGURE 2 is a partial sectional view in elevation of the lower shoulderassembly in position on the drill collar;

FIGURE 3 is a sectional view, taken along the line 3 3 of FIGURE 2;

FIGURE 4 is a partial sectional View of a first alternative shoulderassembly;

FlGURE 5 is a View in elevation of a second alternative shoulderassembly; and

FIGURE 6 is a partial view, taken along the line 6-6 of FIGURE 5.

Various types of stabilizer lbushings, sometimes termed boots, bearingsor bushings are well known to the art and are formed from variousmaterials and in various configurations. For example, such bushings arecommonly formed of rubberor elastomeric material molded about a metalcylindrical sleeve such that the inner cylindrical surface and outercylindrical surface are rubberbearing surfaces. Some rubberconfigurations use strips of aluminum or other metal at the exteriorwear surfaces.

The present invention is equally applicable to all such stabilizerbushings mentioned above so long as the bushing `is of the type whichremains in a substantially nonrotating condition relative to the wallsof the hole while the drill string rotates within the bushing. kForpur-poses of illustration, a bushing formed as a steel cylinder 10 withradially extending ribs 11 is shown. The ribs 11 are spirally formedabout the outer surface of the steel cylinder 10 and extend to themaximum diameter of the bushing which is approximately equal to thediameter 14 of the hole being drilled. The drill collar section 15 ofthe drill string extends upwardly from the bit 16 and is formed of drillcollars threadably interconnected and joined to the drill pipe 17 whichextends upwardly therefrom. The drill collar section 15 is ofsubstantially uniform diameter throughout its entire lengt-h.

The bushing 10 has an inside diameter substantially equal to but greaterthan the outside diameter of the drill collar such that when placed onthe drill collar it is freely rotatable with respect thereto. Inaccordance with the present invention, the bushing 10 is positioned onthe surface of the drill collar between spaced-apart shoulders 20 and 21defined by lremovably aflixed upper and lower shoulder members 23 and24, respectively.

Each of the shoulder members 23 and 24 is adapted to `frictionallyengage the surface of the drill collar section 15. The upper and lowermembers 23, 24 are identical except that the lower member 24 is shown asdefining a series of indentations 27 in its shoulder 21 to provide ameans for moving the bushing 10 into nonrotating engagement with thedrill string. This is done by moving the bushing 10 downwardly, untilindentations on `the lower edge 28 of the bushing engage theindentations 27 in the shoulder. Washover operations can then be carriedout if necessary.

As shown in FIGURES 2 and 3, shoulder member 24 includes a sleeve 30 andsocket 31. The sleeve 30 is cylindrical in configuration with an insidesurface 32 matable with the exterior surface of the drill collar section15. The sleeve has an outside surface 33 of a iirst diameter extendingfrom the bearing shoulder 21 and a second portion 34 of second outsidediameter with a transverse stop surface 35 between. The second portion34 has male threads 36 throughout its length. Extending longitudinallyfrom the male threads 36 on second portion 34 is a tapered portion y38having a maximum Wall thickness adjacent the threaded portion whichresults in an outside surface 40 of maximum diameter less than the rootdiameter of the male threads 36 on second portion 34. The taperedportion 38 tapers to a minimum Wall thickness at the lower end 42 of thesleeve 30. In its normal or relaxed condition, the diameter of theinside surface 32 of sleeve 30 is substantially uniform throughout itslength but the inside surface 44 of the tapered portion 38 is preferablyserrated, knurled or rubber lined to provide maximum Y frictionalengagement with drill collar element 15.1V A

eter approximately equal to the diameter of the lirst outside surface 33of sleeve 30. The socket has female threads 48 along the inner surface50 and this threaded section is matable with the male threads 36 of thesleeve 33. The threads are engageable to the point at which the upperend 52 of the socket 31 engages the stop surface 35 on sleeve 33.Extending longitudinally from the threaded portion is a female taperedsurface 54 matable in interfering engagement with the outside `surfaceof tapered portion 38: That is, the maximum inside diameter of theinside tapered surface 54 is adjacent the threads 4S and is less thanthe maximum diameter` of the male taper 38 in the relaxed condition byan amount suflicient to cause the male taper to be forced inwardly.Similarly, the inside diameter at the minimum point of the female tapersection 56 is less than the minimum outside diameter of the male tapersection 38. Thus, yif'the threads are fully engaged, the male tapersection 38 is forced inwardly by the amount of interference in the taper'diameters` A series of suitable Spanner wrench openings 50, or othermeans for threading the sleeve and socket into engagement, are provided.

As an illustration of the relative sizes of the various parts, la 6%drill collar in one embodiment of the present invention utilizes ashoulder assembly which is 5 in overall length, of which a 1 section isof the first diameter of the sleeve, a 2" length is of the engagedthreads, and a 2 length is of the tapered port-ions. The taper utilizedi-s from 1 to 2 inches per foot of length.

Thus in utilizing the present invention, the lower shoulder assembly 24is slipped over the upper` end of the drill collar at a convenient pointand is lowered to the position at which the shoulder 21 is yat thelowermost point of travel desired for the bushing 10. The sleeve andsocket of shoulder element 24 are then threaded `into engagementsuiiiciently to cause the inside surface 44 ofthe male tapered portion38 of the sleeve to be forced into engagement with `the drill collar toa suiicient extent to bind the shoulder assembly 24 in longitudinalnon-rotational engagement with the drill collar. When suicientfrictional engagement is achieved, a set screw 51 0r other similar meansis used to lock the sleeve vand socket in the engaged position. Thebushing 10 is then slipped onto the drill collar an-d allowed to come torest on the lower shoulder 21. The upper shoulder member 23 `isthereafter slipped onto the drill collar with the bearing shoulder 20downward in the orientation of the drill string shown in FIGURE 1. Theshoulder 20 is spaced from the shoulder 21 by ra suitable distance toallow the desired travel of the bushing l10 between the shoulders. Thesleeve and socket of the upper shoulder member 2-3 are then threadedinto engagement until the surface` 44 of the tapered portion 38 of thesleeve againcomes into frictional engagement with the drill collar to anextent suliicient to prevent movement of the drill collar. The socketand sleeve of the upper shoulder member 23 are then locked in suchengagement by the set screw or other suit-` table means 51.

Thus, it can be seen that the stabilizer `assembly in accordance withthe present invention -is placed on the drill collar at any point alongthe length thereof and is so positioned Without uncoupling 'any portionof the drill collar at an undesired point. By means of thepresentinvention, the drill collar stabilizer is located upon the drillcollar without the .necessity of an additional tool'body being `insertedbetween sections of the drill string.` The means for retaining thestabilizer in position in accordance n with the present invention issuch as to not cause damage above. In the embodiment of FIGURE 4,however, the sleeve member is formed into separate parts with an innersleeve portion defining the bearing shoulder 60 and first diameterportion 61 with a stop surface 62 between the outer diameter and a malethreaded portion 63. The tapered portion 64 of the sleeve is separablefrom the inner portion thereof and is adapted to be in abuttingrelationship at its upper surface or end 65 with the lower end surface66 of the inner sleeve portion. The tapered portion 64 has an outertapered surface 65A and an inner friction engaging surface 67 which isshown in the relaxed condition, and when in such relaxed condition hasan inside diameter substantially equal to the diameter of the drillcollar so that it may be easily positioned thereon. The socket 68 has afemale threaded portion 69 extending from the inner end surface 70thereof and is threadable to the point at which the end surface 7l)engages the transverse surface 62. A female tapered surface 71 isprovided in the socket with a taper which is matable with the outsidetapered surface 65A of the sleeve, but with interfering dimensions suchthat when it is moved longitudinally along the sleeve it causes thesleeve to be moved radially inwardly. Radially inward movement of thetapered portions 64 of the sleeve is allowed by a longitudinal slot 73provided through the wall of the sleeve to allow its diameter to bereduced. A skir-t portion 75 of -the socket extends downwardly below thetapered portions thereof and includes means, such as -spanner wrenchopenings 76, for engaging the socket and sleeve into threadedconnection.

A second alternative embodiment is shown in FIG- URES and 6 whichdiffers from the shoulder members previously described. The -shouldermember of this embodiment is of one piece `only without interferingtapers a-s in the previously described embodiments. Thus, as shown inFIGURIES 5 and 6, the shoulder providing member 80 `of this embodimentis generally cylindrical in configuration with an inside diameter -81substantially equal to but greater than the outside diameter of thedrill collar such that it is matable therewith. The cylinder is splitlongitudinally at one point in its circumference by a slot 82 whichextends the full length of the cylinder.

'Ihe inside diameter 81 and outside diameter 83 of the member 80 aresubstantially constant, and the decrease in diameter in this embodimentis provided by forcing the surfaces 85 and 86 of the slot 82 toward oneanother by fastening means, such as bolts or screws. Thus, as shown inFIGURES 5 and 6, a series of longitudinally spaced tangentialindentations 87 are provided at opposite sides of the slot 82 in astaggered arrangement throughout the length of the slot; that is, theindentation 87A is at one side of the slot 82 and is formed to provide abearing surface 88 with a female` threaded opening 89 extendingtherefrom to the slot and into the wall of the cylinder at the oppositeedge of the slot. A screw can then be threaded into the female threadedopening 89 at both sides of the slot, brought into engagement with thebearing surface 88, and tightened further to draw the surfaces 85 and 86of the slot together. rIlhe indentation 87B is longitudinally spacedtherefrom at the opposite side of the slot 82 and so forth throughoutthe length of the slot.

The shoulder member 80 of FIGURES 5 and 6 is brought into engagementwith the drill collar, to provide a bea-ring shoulder 90 comparable tothe bearing shoulders and 21 previously described, by placing it uponthe ydrill collar in its relaxed condition, inserting the screws intoeach of the indentations 87, and then tightening the screws until theslot 82 is closed to thereby tightly engage the shoulder member 80 uponthe drill collar.

From the foregoing it will be apparent to one skilled in the art thatvarious modifications in the construction and arrangement of parts ofthe present invention can be made. For example, the tapered surfaces inembodiments suoh as shown in FIGURE l can be incorf5 ponated into thethreaded portion by forming a split, tapered, threaded male section. Inconnection with the present invention it has also been found that asteel bushingrhaving `an inner surface of rubber is particularlysuitable.

Thus, the present invention discloses an improved drill collarstabilizer apparatus in which two shoulder forming means are removablyaiiixed to the exterior surface of the drill collar with the shouldersspaced Iapart Ialong the length of the drill collar and with astabilizer bushing positioned therebetween.

What is claimed is:

1. A drill string stabilizer assembly comprising in combination:

a drill string section having a cylindrical exterior wall;

a Ycylindrical bushing `rotatably positioned upon the cylindricalsurface of the drill string section; a first shoulder defining means,means for releasably securing said shoulder defining means to saidcylindrical surface, said shoulder defining means being juxtaposed toone end of said bushing and havin-g a diameter greater `than the insidediameter of said tbushing to limit the longitudinal travel of saidbushing in one direction; and a second shoulder defining means, meansfor releasably securing said shoulder defining means to said cylindricalsurface, said second shoulder defining means being juxtaposed but spacedfrom the opposite end of said bushing to limit the longitudinal travelthereof in the direction opposite said one direction.

2. A drill string stabilizer comprising in combination:

a drill collar having a cylindrical exterior surface;

ya cylindrical bushing rotatably positioned upon the cylindrical surfaceof said drill collar 'and having radially extending ribs extending fromthe outer surface thereof;

a first shoulder defining means removably afi'ixed to said cylindricalsurface for limiting longitudinal travel of said bushing in onedirection;

a second shoulder defining means removably aixed to said cylindricalsurface and spaced from the opposite end of said bushing to limitlongitudinal travel thereof in the opposite direction;

.at least one of said shoulder defining means including a sleeve havingan inside surface engageable with said cylindrical surface of said drillcoll-ar, said sleeve having a portion of its outer surface having malethreads thereon, a male tapered portion extending from said portionhaving male threads, said male tapered portion having an outside surfacehaving its greatest diameter nearer said portion having male threads andhaving its outside surface having its least diameter at the end thereofremote from said portion having male threads, slots extendinglongitudinally through said male tapered portion, said male taperedportion having a friction inner surface engaging said cylindricalsurface of said drill collar; and

a socket having female threads on the inner surface thereof engageablewith the male threads of said sleeve, said socket having a femaletapered portion engageable with said male tapered portion, whereby whensaid sleeve and said socket are threadedly engaged said friction innersurface of said male tapered portion frictionally engages said drillcollar.

3. A drill string stabilizer comprising:

a drill collar having a cylindrical exterior surface;

a cylindrical bushing rotatably positioned upon the cylindrical surfaceof the drill collar;

a first shoulder defining means removably affixed to said cylindricalsurface to limit longitudinal travel of said bushing in one direction;and

a second shoulder defining means removably affixed to said cylindricalsurface and spaced from the opposite end of said bushing to limit thelongitudinal travel thereof in an opposite direction;

said shoulder dening means comprising `cylindrical sleeves positioned-over said drill collar and having an inner surface portion frictionallyengageable with said drill coll-ar and releasable means for exerting aninwardly directed force upon the frictional portion to thereby removablyposition said shoulder deining means against longitudinal movement.

A drill string stabilizer comprising:

drill collar having a cylindrical exterior surface; cylindrical bushingrotatably positioned upon the cylindrical surface of said drill collar;

rst shoulder defining means removably axed to said cylindrical surfaceto limit the longitudinal travel of said bushing in one direction; A

second shoulder defining means removably aHiXed to said cylindricalsurface to limit the longitudinal travel of said bushing in the oppositedirection,

said shoulder defining means including a sleeve with -a male taperedportion having an inside surface in engagement with the outer surface ofsaid drill collar, a socket having a female tapered portion engagingsaid male tapered portion of said sleeve, said socket and sleeve -havingthreaded connections whereby longitudinal -movement of said socket inone direction causes greater inward gripping force by said male sleeve.

References Cited by the Examiner UNITED STATES PATENTS Mack 308-4 Putman308-4 Hoffman 30S-237 Nelson 285-323 X Lane 30S-4 Kamerer 30S-4 snub285-323 X Wright. t

Hanes 287-5204 Wright 308-4 Parky 166-243 X` Lee 285-323 kDAVID I.WILLIAMOWSKY, Primary Examiner.

FRANK SUSKO, Examiner .L. L. JOHNSON, Assistant Examiner.

4. A DRILL STRING STABILIZER COMPRISING: A DRILL COLLAR HAVING ACYLINDRICAL EXTERIOR SURFACE; A CYLINDRICAL BUSHING ROTATABLY POSITIONEDUPON THE CYLINDRICAL SURFACE OF SAID DRILL COLLAR; A FIRST SHOULDERDEFINING MEANS REMOVABLY AFFIXED TO SAID CYLINDRICAL SURFACE TO LIMITTHE LONGITUDINAL TRAVEL OF SAID BUSHING IN ONE DIRECTION; A SECONDSHOULDER DEFINING MEANS REMOVABLY AFFIXED TO SAID CYLINDRICAL SURFACE TOLIMIT THE LONGITUDINAL TRAVEL OF SAID BUSHING IN THE OPPOSITE DIRECTION,SAID SHOULDER DEFINING MEANS INCLUDING A SLEEVE WITH A MALE TAPEREDPORTION HAVING AN INSIDE SURFACE IN ENGAGEMENT WITH THE OUTER SURFACE OFSAID DRILL COLLAR, A SOCKET HAVING A FEMALE TAPERED PORTION ENGAGINGSAID MALE TAPERED PORTION OF SAID SLEEVE, SAID SOCKET AND SLEEVE HAVINGTHREADED CONNECTIONS WHEREBY LONGITUDINAL MOVEMENT OF SAID SOCKET IN ONEDIRECTION CAUSES GREATER INWARD GRIPPING FORCE BY SAID MALE TAPEREDPORTION AND LONGITUDINAL MOVEMENT OF SAID SOCKET IN THE OPPOSITEDIRECTION CAUSES A RELEASE OF THE MALE TAPERED PORTION TO PERMIT REMOVALOF SAID SLEEVE.